The invention concerns a flexible, armoured pipe comprising an inner liner and a spirally-wound pressure amour surrounding said inner liner, said pressure amour comprising a number of adjoining armour profiles, each of said profiles having a number of recesses, at least two of said recesses being provided along surfaces of said adjoining armour profiles forming a cavity therebetween, and a number of locking profiles, said locking profiles being adapted to hold together said adjoining profiles.
The invention also concerns use of the pipe for transport of fluids.
Pipes of the above-mentioned type normally comprise an inner barrier layer, the so-called inner liner, which forms a barrier against the out-flow of the fluid which is desired to be transported through the pipe. Moreover, pipes of the above-mentioned type comprise an outer barrier layer, the so-called outer liner, which prevents the surrounding environment from influencing the space in between the inner and the outer liner.
On the outside of the inner liner one or more armouring layers are wound, which are not chemically bound to the remaining components of the pipe, but can move in relation to these, which ensures the flexibility of the pipe during laying-out and operation.
The whole of the pipe armouring is most often placed between the inner and the outer liner, but in certain cases only a part of the armouring layers will be placed between the inner and the outer liner, while the remaining part of the armouring is placed outside the outer liner. When a part of the armouring lies outside the outer liner, an additional layer can be applied to the outside of the pipe with the object of protecting the outermost armouring layer against mechanical damage.
In order to prevent the collapse of the inner liner, the inner side of this is often lined with a flexible, wound, permeable pipe, a so-called carcass.
The above-mentioned type of flexible pipe is used, among other things, for the transport of fluids and gases in different depths of water. They are used especially in situations where very high or varying water pressure exists along the longitudinal axis of the pipe. As an example can be mentioned riser pipes which extend from the seabed up to an installation on or near the surface of the sea. Pipes of this type are also used between installations, which are located at great depths on the seabed, or between installations near the surface of the sea.
Some of the armouring layers are wound with a great angle relative to the longitudinal direction of the pipe, and will therefore primarily be able to absorb the radial forces that arise as a result of outer or inner pressure. The profiles thus prevent the collapse or rupture of the pipe as a result of pressure influences and are therefore called pressure armour.
The pressure armour will always lie in the space between the pipe""s inner and outer liner, and is most often built up of different profiles in metal.
In that very high inner pressure can exist inside the pipe, a mutual anchoring of the pressure-bearing profiles is of great importance, since a slipping of these along the axis of the pipe can result in too great a mutual profile distance with damage of the inner liner as a consequence. The mutual mechanical anchoring is achieved by configuring the profiles in such a manner that they lock together mechanically when they are wound.
In order to ensure the flexibility of the pipe, the pressure armour layer is designed so that a limited mutual movement of the pressure-bearing profiles is permitted.
Unlike the pressure armour, profiles, which are wound with a small angle in relation to the longitudinal axis of the pipe, will not be able to absorb radial forces to any significant degree, but on the other hand are able to absorb forces exerted along the longitudinal axis of the pipe. In the following, this type of armouring will be referred to as tension armour, in that its primary task is to absorb tensile forces as a result of inner pressure in the pipe and its suspension. The tension armour is placed either in the space between the inner and the outer liner, or on the outside of the outer liner.
Under certain conditions of operation, the pipe will be exposed to compressive, axial forces, which will compress the pipe. Providing that the tension armour is prevented from expanding radially, it will be able to absorb these compressive forces. However, if the pipe is constructed in such a manner that the radial expansion of the pipe""s tension armour is not prevented, the tension armour will not be able to absorb the compressive, axial forces, in that these will be absorbed primarily by the inner and the outer liner. This compression can continue until the free volume between the pressure armour profiles is used up, after which the compressive, axial forces will be absorbed primarily by the pressure armour, which is made of a material with far greater rigidity than the inner and outer liner. In this connection it is a problem that the pressure armour is not stable in compression, the reason being that the pressure armour profiles will have a tendency to slide out over each other with subsequent damage to the pipe.
WO00/09930 discloses a tubular, flexible pipe comprising an inner sealing sheath of polymer, a cylindrical pressure vault comprised of a helical wire winding with gaps between windings. The vault comprises elongated masking elements at least partially masking the gaps between the winding of the wire and being at the inner sheath, whereby it is obtained that the problem of xe2x80x9cinternal sealing sheath creepxe2x80x9d is allegedly solved.
U.S. Pat. No. 2,087,876 discloses a self-supporting, flexible, annular strand without a pressure amour and without internal supporting means intended for use as a hollow conductor for high voltage transmission of electric energy, said strand comprising a plurality of helically arranged strips in edge-to-edge relationship to form a tubular structure and wires interposed between and separating edges of said strips, said strips being laterally separable and able to pivot on said wires. The wound strips have a small angle relative to the direction of the pipe, whereby radial forces on the strand open the strips and result in radial forces not being absorbed, i.e. a quite different result than that of the present invention.
It is an object of the present invention to provide a new configuration of pressure armour profiles that prevents the profiles from sliding out over each other.
It is also an object of the invention to increase the barrier characteristics of the pressure armour, which in certain cases can considerably increase the functionality of the finished pipe.
The objects of the invention are achieved in that at least two recesses are locking recesses and that said formed cavity accommodates a locking element.
Means are thus provided in the armouring for the prevention of uncontrolled, radial displacement of the primary, spirally-wound profiles. Moreover, means are provided in the armouring, which prevent a free, or almost free flow between the concave and the convex side of the armouring. Furthermore, the primary, spirally-wound profiles are provided with at least two recesses in which a profile of another kind is placed, whereby a locking of the primary, spirally-wound profiles against mutual, uncontrolled, axial displacement is achieved.
In a most preferred embodiment the profile is configured as a K-profile with four recesses. A locking against uncontrolled, radial displacement is hereby achieved, in that at least two recesses are provided along adjoining surfaces in K-profiles, and in that a locking element is arranged in the space which is formed by the two adjoining recesses.
In other words, the configuration of the armouring according to the invention distinguishes itself from hitherto-known pressure armouring by a mutual locking of the K-profiles, not only along the axial direction of the pipe, but also at right-angles hereto, which can be attributed to the use of locking profiles and locking elements with different functions.
In another embodiment, the K-profile has two recesses which are arranged in the corners of the profile, and that an I-profile is provided in the cavity which is formed by the two recesses in adjoining profiles, whereby it is ensured that in the event of great pressure influences, there is no migration of material, e.g. inner liner material, into the spaces which exist between the profiles.
Preferred embodiments with various locking elements include, in a non-limiting way, locking elements that wholly or partly fill out the cavity, locking elements that are configured as an I-profile, recesses that are semicircular in shape, and locking elements that are configured with a substantially circular cross-section.
In another embodiment the locking element is made of an elastic, deformable material, and an essential barrier against migration of fluids between the concave and convex parts of the armoring is achieved, which can give the armoring an important extra functionality when the locking profile is configured so that the deformation of this is necessary for it to be accommodated in the adjoining recesses.
In another embodiment, by configuring the locking element as a wire with a C-shaped cross-section, it is ensured that a longitudinal channel is provided which, for example, can be used for the leading away of undesired fluids or the supply of cleaning liquids or the like.
Further embodiments of the invention include, in a non-limiting way, locking elements that are configured as a wire with a O-shaped cross-section, locking profiles that are C-shaped, profiles that consist of a material which is wholly or partly made of a metal, a metal alloy or a ceramic-reinforced metal material, profiles that consist of a material which is wholly or partly made of a polymer or an armored polymer, and inner liners that surround a carcass, the carcass being configured as a pressure armor.
As mentioned, the invention also concerns a use of the pipe. This use involves, for example, transporting fluid such as water, ammonia, or hydrocarbons, with the flexible, armored pipe.